Optical alignment apparatus



2 Sheets-Sheet 1 Filed Sept. 29, 1966 INVENTOR. Nat/700D. Lev/n iusw 6mMarch 3, 1970 N. D. LEVIN 3,498,722

' OPTICAL ALIGNMENT APPARATUS Filed Sept. 29, 1966 2 Sheets-Sheet 2INVENTOR.

Na/h on D. Lev/n United States Patent 3,498,722 OPTICAL ALIGNMENTAPPARATUS Nathan D. Levin, Highland Park, Ill., assignor to AdmiralCorporation, Chicago, Ill., a corporation of Delaware Filed Sept. 29,1966, Ser. No. 583,018 Int. Cl. G01b 11/26; G02b 21/18 U.S. Cl. 356138 8Claims ABSTRACT OF THE DISCLOSURE A device for accurately and quicklyaligning a color picture tube lighthouse lens assembly including anaccurately locatable baseplate carrying a plurality of microscopesvertically oriented with respect to a corresponding plurality ofreference marks on the lens assembly. The microscopes are preciselyfocused on the reference marks of a lens assembly in a lighthouse knownto be in prop r alignment, whereafter the baseplate with microscopesaffixed may be moved to another lighthouse for quickly and accuratelyaligning the lens assembly thereof.

This invention relates in general to alignment apparatus and inparticular to optical alignment apparatus for picture tube lighthouses.

Picture tubes of the shadow mask variety are in widespread use in todayscolor television receivers. Typically, picture tubes of this typecomprise a glass envelope consisting of a funnel and a face panelsecured together, an electron-sensitive phosphor screen on the inside ofthe face panel, an aperture mask fixed close behind the phosphor screen,and an electron gun assembly mounted in the neck of the picture tubefunnel. The electron sensitive phosphor screen usually comprises a largenumber of individual phosphor dots grouped in triads. Each of the triadsincludes phosphor dots of three primary colors, e.g., red, blue, andgreen. Corresponding to each of these phosphor dot triads is a singleaperture in the shadow mask. The electron gun assembly usually comprisesthree individual electron guns arranged in a delta fashion for producingthree separate electron beams.

In operation the three electron beams are scanned across the screen. Thebeams pass through the apertures in the shadow mask and strike thephosphor dots on the screen. In Order to produce a picture with colorpurity, it is necessary to have the electron beam from each one of thethree electron guns strike only its associated color phosphor dot ineach triad. In other words, the electrons from the blue gun shouldstrike only the blue phosphor dots, and so on. Thus it is apparent thatthe accu-,

rate positioning of each phosphor dot with respect to the shadow maskaperture associated with it and also with respect to the source of itsassociated electron beam is very critical.

The phosphor dots on the face panel are produced on aone-color-at-a-time basis. This can be accomplished by slurrying alight-sensitive emulsion containing phosphor powder of a particularcolor, blue, for example, on the inside surface of the face panel andthen exposing the emulsion to a light source using the apertured shadowmask as a negative. The light beams passing through the individualapertures strike the light-sensitive emulsion, thereby causing theemulsion and blue phosphor powder to adhere to the face panel. Theunexposed portion of the emulsion is then washed off, leaving bluephosphor dots only in the areas exposed to the light. This process canthen be repeated two additional times to produce red and green phosphordots.

Each operation of exposing the light-sensitive emulsion is usuallycarried out by employing a lighthouse ar- 3,498,722 Patented Mar. 3,1970 rangement which includes a collimator assembly, a lens assembly,and a panel support assembly. The collimator assembly includes a sourceof light and a collimator having a small tip to simulate a point lightsource. The lens assembly includes a lens and a lens holder to supportthe lens above the collimator tip. The panel support assembly supportsthe picture tube face panel above the lens assembly and collimatorassembly. The lighthouse arrangement, particularly the lens, is designedso that when the collimator assembly, the lens assembly, and the panelsupport assembly are properly positioned with re spect to each other thepaths of the light beams from the lens to the face panel on the panelsupport assembly simulate the paths of the electron beam from one of theelectron guns during operation of the picture tube. It is well-knownthat many ditferent lens designs can be employed in a lighthousearrangement to accomplish the required light-optical analogy to electornbeam travel, but n every case it is vital that the collimator assembly,the lens assembly, and the panel support assembly be accurately aligned.

Since it is necessary to produce picture tubes on a mass productionbasis, it is most common to employ a group of lighthouse arrangements toexpose the same set of phosphor d ts on numreous picture tube panels.Furthermore, since it is also common to employ a separate lighthousearrangement for each of the three sets of color phosphor dots on aparticular picture tube panel, three groups of lighthouse arrangementsare required. Each of the lighthouse arrangements Within a particulargroup must have its alignment of collimator assembly, lens assembly, andpanel support assembly as nearly identical as possible to the alignmentof the corresponding assemblies in other lighthouses in order that aninterchangeable product will result. Moreover, this requirement ofinterchangeability is even more stringent with three groups oflighthouse arrangements since interchangeability must ex st among alllighthouses in a particular group with respect to all lighthouses in theother groups.

In the past it has been necessary to align each of the lighthouses on anindividual basis. This involved manipulating the assemblies and checkingthe light beam landings on a reference face panel to determine whetherthe light beams are striking the face plate at points which wouldproduce correctly positioned phosphor dots. Obviously this procedure isextremely time consuming and highly unlikely to result in correspondingalignment from lighthouse to lighthouse with the degree of accuracyrequired for a completely interchangeable product.

Therefore, it is the principal object of this invention to providealignment apparatus for use in accurately reproducing the alignment of aplurality of individual elements.

It is a further object of this invention to provide alignment apparatusfor accurately recording the alignment of a reference lighthousearrangement in an optical manner.

This invention features alignment apparatus which can be used toreproduce the alignment of a plurality of individual elements orassemblies where each of the elements has at least one accuratelypositioned reference point associated therewith.

In a preferred embodiment thereof this invention features an opticalalignment apparatus for picture tube lighthouse arrangements whichenables the accurate reproduction of the alignment of the collimatorassembly, lens assembly, and panel support assembly in a referencepicture tube lighthouse arrangement.

The optical alignment apparatus of this invention generally comprises aflat plate having a configuration that simulates the dimensions of apicture tube face panel and a plurality of individual microscopeassemblies mounted on the plate. The flat plate is adapted to be mountedon the panel support assembly of the reference picture tube lighthousearrangement and the individual microscope assemblies are positioned onthe fiat plate so that they can be focused on individual referencepoints associated with the collimator assembly and lens assembly. Inthis manner the alignment apparatus records the alignment of thecollimator assembly, lens assembly, and panel support assembly in thereference picture tube lighthouse arrangement with microscopic accuracyand can be used to duplicate this alignment in other lighthousearrangements having corresponding assemblies.

The advantage of using the optical alignment apparatus of this inventionis apparent since it facilitates the duplication of the alignment in areference lighthouse arrangement with minimum time and effort andmaximum accuracy.

Other objects, features, and advantages of this invention and a completeunderstanding thereof will be gained from a consideration of thefollowing description in conjunction with the accompanying drawings inwhich:

FIG. 1 is an exploded perspective view of a lighthouse arrangement withan alignment device in accordance with this invention.

FIG. 2 is a perspective assembly view of a lighthouse arrangement withan alignment device according to this invention.

FIG. 3 is a view of the alignment apparatus taken along the lines 33 inFIG. 2.

FIG. 4 is a view taken along the lines 4-4 in FIG. 2, looking into theeyepiece of one of the microscopes.

In FIG. 1 a lighthouse arrangement including a collimator assembly 20, alens assembly 30, and a panel support assembly 40, is shown inconjunction with an alignment device 50 constructed in accordance withthis invention. A structure composed of plate 10, four columns 12, andtable 11 with a rectangular opening 14 therein provides support forcollimator assembly 20, lens assembly 30, and panel support assembly 40.

Collimator assembly includes a light source 21 and a light collimator 22which has a tip 23 projecting through aperture 25 in plate 24 at the topof collimator assembly 20. As shown collimator assembly 20 is mounted inhole 15 in plate 10.

Lens assembly includes a lens holder 31 and a lens 32. Lens 32 fits intoan aperture 37 in lens holder 31 and rests on a lip 38. Two lens holderpins 39 can be inserted through holes 36 in lens holder 31 and throughholes 17 in plate 10 to fix the position of the assembly 30 on plate 10.Two cross marks 34 provide reference points for lens assembly 30, thefunction of which will be described later.

Panel support assembly 40 comprises a support table 41, three panellocating blocks 42 mounted on support table 41, and three panel supportblocks 44 also mounted on support table 41. Two mounting pins 47 may beinserted through holes 46 in support table 41 and through holes 18 intable 11 to secure panel support assembly 40 in a particular position ontable 11.

Alignment apparatus 50 consists essentially of a support means, shown asa flat plate 51, and an optical means comprising three individualmicroscope assemblies 52, 53, and 54. Mounting blocks are fastened onthe underside of flat plate 51 in positions corresponding to panelsupporting blocks 44 on support table '41. Microscope assemblies 52, 53,and 54 are mounted on fiat plate 51 in three apertures 56. Eachindividual microscope assembly is secured in apertures 56 by a pair ofmounting fingers 57. Apertures 56 are large enough to accommodate themicroscope assemblies in various positions. Each microscope assembly hasan eyepiece 60, a focus adjustment mechanism 59, and an auxiliary lenssystem 58 to increase the focal length.

Lens 32 is shown inserted in lens holder 31. Panel support assembly 40is secured in position on table 11 by mounting pins 47. Flat plate 51 isindexed on panel support assembly 40 by panel locating blocks 42 withblocks 55 mounted on panel supporting blocks 44. Microscope assemblies52, 53, and 54 are positioned in apertures 56 so that microscopeassemblies 52 and 54 can be focused on cross marks 34 on lens assembly31 and microscope assembly 153 can be focused on collimator tip 23 incollimator assembly 20. This is shown by the center lines drawn throughthe individual microscope assemblies to the particular reference pointson which they are focused. The reasons for this focusing on referencepoints associated with the collimator assembly 20 and lens assembly 30will be discussed in greater detail below.

In FIG. 3 a top view of alignment apparatus 50 in position on panelsupport assembly 40 is shown. In this view the indexing of fiat plate 51on panel support assembly 40 by panel locating blocks 42 is clearlyshown. Plate 51 simulates in configuration a picture tube face panel,the perimeter of which is shown by dotted lines 80. In this view it isalso clearly shown that microscope assemblies 52, 53, and 54 can belocated in various positions within apertures 56. Of course, apertures56 are located on plate 51 with general reference to the positions ofthe reference marks associated with collimator assembly 20 and lensassembly 30 which are shown in FIGURES 1 and 2.

In FIG. 4 a view of the top of microscope assembly 53 is shown. One ofthe lenses 62 in microscope assembly 53 is shown with an appropriatereticle such as crosshair 63 thereon. It is to be understood that eachof the other microscope assemblies 52 and 54 have corresponding lenseswith appropriate rectiles thereon.

Referring back to FIG. 2 in combination with FIG. 3, it is apparent thatalignment apparatus 50 can be used to record in a very accurate mannerthe relative alignment of panel support assembly 40, lens assembly 30,and collimator assembly 20. By positioning microscope assemblies 52 and54 so that the reticle in each is accurately focused on one of the crossmarks 34 on lens assembly 31, the position of panel support assembly 40with respect to lens assembly 30 is accurately recorded. By positioningmicroscope assembly 53 so that its reticle focuses exactly on collimatortip 23, the position of panel support assembly 40 with respect tocollimator assembly 20 is accurately recorded.

At this point it is to be understood that alignment apparatus 50 must befirst set up with respect to a reference lighthouse arrangement, that isto say, with respect to a lighthouse arrangement in which the alignmentof collimator assembly 20, lens assembly 30, and panel support assembly40 has been previously determined by a trial and error method. Thismethod usually involves placing a reference face panel on supportassembly 40 and manipulating the position of lens assembly 30 and panelsupport assembly 40 until the light beam landings on the reference facepanel are correctly positioned. This is a timeconsuming procedure andmust be done very carefully to insure that properly positioned phosphordots will be produced on subsequently exposed face panels. Once theproper position of lens assembly 30 is determined, lens holder 31 isfixed in position on plate 10 by lens holder pins 39. Panel supportassembly 40 is also secured in its correct position on table 11 bymounting pins 47.

Since a separate lighthouse arrangement is used for each set of phosphordots to be developed on a particular face panel, two other referencelighthouses would also have to be set up by the same trial and errormethod. Having now a reference lighthouse arrangement for each set ofphosphor dots, alignment apparatus 50 can be used to record in amicroscopically accurate manner the alignment of collimator assembly 20,lens assembly 30, and panel support assembly 40 in the referencelighthouse arrangement in the manner described above. Oncethe alignmentof the three constituent-assemblies in a reference lighthousearrangement has been .recordediby'alignment apparatus 50, the apparatus"can be transferred to a panel support assembly 40 of a secondlighthouse arrangement which has not yet been aligned and can be used asan aid in reproducing the reference alignment. Obviously, collimatorassembly 20, lens assembly 30, and panel support assembly 40 in thesecond lighthouse arrangement must be very nearly identical inconstruction to the corresponding assemblies in the reference lighthousearrangement, and reference marks 34 on lens holder 31 must be located inthe same position relative to lens 34 as they were on the correspondinglens "holder in the reference lighthouse arrangementT hen, with flatplate 51 of alignment apparatus 50 indexed by panel cating blocks 42 onpanel support assembly 40 of the second lighthouse arrangement, supporttable 41 can be manipulated on table 11 until, looking into microscopeassembly 53, collimator tip 23 is accurately centered in thecross-hairs. Panel support table 41 can then be. secured on table 11 bydrilling the holes 46 and 18 shown in FIG. 1 and inserting mounting pins47 therein. This fixes panel support assembly 40 with respect tocollimator assembly 20 in the same relative position as in the referencelighthouse arrangement. Lens holder 31 may then be moved around on plate10 until the cross-hairs in microscope assemblies 52 and 54 areaccurately centered on cross marks 34. Panel support assembly 30 is thenin proper position with respect to both collimator assembly 20 and.panel support assembly 40 and can be fixed in that position by drillingthe holes 36 and 17 shown in FIG. 1 and inserting lens holder pins 39therein. It is obvious that this same alignment procedure, usingalignment apparatus 50, can be utilized to align as many othercorresponding lighthouse arrangements as are desired.

From the above description of an alignment apparatus in accordance withthis invention it is apparent that such an alignment apparatusfacilitates the microscopically accurate recording of the alignment of areference lighthouse arrangement and the duplicating in an exact mannerof the reference alignment in any number of corresponding lighthousearrangements. The resulting set of lighthouse arrangements meets therequirement of interchangeability to a degree which could not beattained by any alignment procedure used in the past. Moreover, the useof an alignment apparatus constructed in accordance with this inventionresults in improved exposure of phosphor dot triads on mass producedpicture tube face panels and, as a result, the overall quality ofpicture tubes which incorporate face panels exposed on lighthousearrange merits which are aligned by using as an aid an alignment deviceconstructed in accordance with this invention is enhanced.

Successful utilization of alignment apparatus 50 requires thatcollimator assembly 20, lens assembly 30, and panel support assembly 40,each have at least one reference point associated therewith. In thepreferred embodiment described above panel support assembly 40 has,effectively, three associated reference points namely the three panellocating blocks, and the lens assembly has two associated referencepoints-cross marks 34. Collimator assembly 20 has only one referencepoint. The provision of more than one reference point for lens assembly30 increases the accuracy of the alignment procedure, as does theprovision of three reference points for panel support assembly 40.Various other ways of providing associated reference points forcollimator assembly 20, lens assembly 30, and panel support assembly 40would suggest themselves to those skilled in the art. Moreover, with aproper adaptation of microscope assemblies 52, 53, and 54, lighthousealignment device 50 :ould also be used to record and reproduce therequired 6 separations between collimator tip 23, lens 32 and supporttable 41.

It is to be understood that the foregoing description of a particularembodiment of this invention is given for the purpose of illustrationand that numerous modifications could be made without departing from thespirit and scope of this invention as claimed in the following claims.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. Apparatus for use as an aid in reproducing the alignment of aplurality of individual elements, each of said elements having at leastone accurately positioned reference point associated therewith, saidapparatus comprising: support means adapted to be fixed in a particularposition with respect to one of said reference points associated with apredetermined one of said elements; and a "plurality of microscope meansmounted on said support means operable to focus accurately oncorresponding ones of said reference points associated with the othersof said elements when said support means is in said particular position.

2. Apparatus as claimed in claim 1, wherein said plurality of microscopemeans comprises a number of individual microscope assemblies, saidnumber being equal to the total number of said reference points to befocused 3. Apparatus as claimed in claim 2, wherein each of saidmicroscope assemblies includes a lens having a reticle thereon, saidmicroscope assemblies being positioned on said support means so thatindividual ones of said reticles are aligned to focus accurately oncorresponding individual ones of said reference points when said supportmeans is in said particular position, said apparatus thereby recordingaccurately the alignment of said elements.

4. Apparatus for use in conjunction with a reference picture tubelighthouse arrangement having a collimator assembly, a lens assembly,and a panel support assembly aligned in a predetermined manner, saidcollimator assembly and said lens assembly each having at least oneaccurately positioned reference point associated therewith, saidapparatus comprising: support means adapted to be mounted in aparticular position on said panel support assembly; and a plurality ofmicroscope means mounted on said support means Operable to focusaccurately on each of said reference points when said support means ismounted in said particular position on said panel support assembly,whereby said apparatus may be used to duplicate the alignment of saidreference lighthouse arrangement in lighthouse arrangements havingcorresponding collimator, lens, and panel support assemblies.

5. Apparatus as claimed in claim 4, wherein said support means is a flatplate having a particular configuration simulating the dimensions of apicture tube panel; and said plurality of microscope means comprises anumber of individual microscope assemblies, said number being equal tothe total number of said reference points.

6. Apparatus as claimed in claim 5, wherein said fiat plate has aplurality of apertures therein, each of said microscope assemblies beingmounted in an individual one of said apertures with the longitudinalaxes of said microscope assemblies substantially perpendicular to theplane of said flat plate.

7. Apparatus as claimed in claim 6, wherein said apertures in said flatplate are sufficiently large to permit said microscope assemblies to bemounted in various positions therein.

8. Apparatus as claimed in claim 7, wherein each of said microscopeassemblies includes a lens having a reticle thereon, said microscopeassemblies being positioned within their associated apertures so thatindividual ones of said reticles are aligned to focus accurately oncorresponding individual ones of said reference points when said flatplate is mounted in said particular position on said panel supportassembly, said apparatus thereby re 3,498,722 7 8 cording accurately thealignment of said collimator, lens, OTHER REFERENCES and panel supportassemblies in said reference lighthouse Fortune, October 1951,

arrangement.

References Cited RONALD L. WIBERT, Primary Examiner UNITED STATES A S 5T. R. MOHR, Assistant Examiner 749,754 1/1904 Spear 1 US. Cl. X.R.3,081,521 3/1963 Smart et al. 2925.19 350-31

